You mean being fluent in English, not in French? Because if you don't, I don't understand your post.
You are hired by a French agency so 1/you need the papers to be allowed to work in France 2/of course you have to be fluent in French.
Now if you mean being fluent in English, they are supposed to. Or at least for the VIP sections. All the people I met had at least a Master's Degree in modern languages. Now since I was working in the players' area, I haven't met everyone either and I don't know the hostesses who were simply checking tickets at the entrance.
I add that if you want to be a driver for the players, you have to apply to the FFT.